Voltage counterphasing in the SSC low energy booster

Operating the SSC low energy booster (LEB) in a counterphasing mode is necessary because the low total ring voltage (25 kV) required at injection for adiabatic beam capture would otherwise result in cavity multipacting. Each cavity requires greater than 15 kV gap voltage (there are eight single-gap cavities in the LEB) to be free of multipacting. The analysis of the cavities´ behavior in this mode and under time-varying beam loading is presented. It is shown that fast feedback loops with moderate gain are necessary to operate with the available tetrode power. The Robinson instability and the required power and phase histories are discussed